Stratomaster Maxi Single

RV-3

Universal Engine RPM and Rotor RPM display

The RV-3 unit is a 3.5” instrument providing a universal rev counter that can be adapted to a variety of roles. Typical uses are engine RPM displays or Helicopter / Gyroplane Rotor RPM displays.

Digital engine RPM / Rotor RPM display with scale selectable analog display Engine hobbs meter (can be set to current engine time) Engine running timer (can be used as flight timer), resettable to zero at any time.

The main display

Hobbs Run timer meter

Digital RPM display Analog RPM display

About RPM measurements

Generally, there are two different methods of measuring RPM. The RV-3 unit can be setup to perform either method. The first method involves counting pulses generated by some device in the engine or from a sensor in case of Rotor RPM. Pulses are counted over a period of time and the result is then used to calculate RPM. This method requires a high number of pulses and a short measurement interval. The RV-3 counts pulses for ½ second. This method is suitable for most two stroke engines such as produced by Rotax. Engines producing few pulses (perhaps only one pulse per revolution) and run at low revs, as well as slow turning rotors require a different method. Here the RV-3 can use the time it takes to generate only two pulses as bases for the RPM calculation.

The particular method to be used and the number of pulses per revolution are entered as part of the RV-3 setup as given below.

Setting up the RV-3

Press the Menu key to enter the menu. You can move forward and backwards in the menu by using the + and – keys. To change or select a menu item, move the highlight to the desired item and then press the Select (Enter) key. To end an edit or function, press the Menu key again.

To exit the menu and continue normal operation, press Menu again. Note, all changes you have initiated during your session will only be remembered by the instrument if you exit the menu.

Zero FT

This function allows you to set the flight timer to zero. The flight timer counts hours and minutes while the engine is running.

Set Hobbs

This function allows you to set the hobbs meter to your current engine running time.

Use the plus and minus buttons to change the indicated part of the hobbs reading. Use the Select button to change from hour hundreds to hours to minutes. End the edit by pressing the Menu button.

Scale …

Choose your desired scale for the analog RPM display. You can choose values from 500 to 20000 RPM in steps of 500 RPM. You should select a value that is just higher than the highest RPM you expect during operation.

Contrast …

This function allows you to change the display contrast to your liking. You can select values from about 20 to 45.

Backlight …

This function allows you to switch the display backlight on or off.

Pulse …

Select if you want the RV-3 to count pulses from the engine for ½ second period (Fast) or if you want the RV-3 to use the time between pulses to calculate revs (Slow).

Typical setups:

Rotax 503,582 DCDI - Fast (6 pulses per revolution). Rotax 503 single ignition, Rotax 912/914 – Slow (one pulse per revolution). Gyro Rotor RPM with gear tooth sensor – Fast (about 100 pulses per revolution). Gyro Rotor RPM with single hall effect sensor – Slow (one pulse per revolution). Helicopter Rotor RPM with single hall effect sensor – Slow (one pulse per revolution).

Calib …

Enter the number of pulses per RPM. For engines with an uneven number of cylinders like three cylinder four stroke engines you can enter values containing fractions (usually 1.5 in this example). Most four stroke engines would generate one pulse for every two revolutions per cylinder. A four cylinder automotive four stroke engine would thus generate 2 pulses per revolution. A typical Rotax DCDI two stroke engine would generate 6 pulses per revolution. The well known Rotax 912/914 engines generate one pulse per revolution.

Filter …

The RV-3 unit contains a digital filter. This filter is used to achieve a higher resolution of the digital rev counter than is available in ordinary operation. In digital rev counters, resolution is largely dependant on the amount of time given to measure RPM. The more time available, the higher the resolution possible. However, on the downside of this, the more sluggish the display will react to changes in engine settings. Resolution with the RV-3 is dependant on the number of pulses per rev and the type of measurement method you have selected (Pulse Fast/Slow). The update rate for the measurement is a fixed, fast 0.5 seconds. The digital filter is activated whenever input revs are fairly constant and this results in a very high resolution of the digital RPM display in a short time span. The filter needs to be setup for the expected base resolution. This can be between 10 and 30 RPM for most setups. The filter has the following settings:

Scale -The setting is made dependant on your Scale selection from 500 to 20000 RPM. The filter factor is fixed as follows: Scale 500 – 10 RPM Scale 10000 – 200 RPM Scale 1000 – 20 RPM Scale 10500 – 210 RPM Scale 1500 – 30 RPM Scale 11000 – 220 RPM Scale 2000 – 40 RPM Scale 11500 – 230 RPM Scale 2500 – 50 RPM Scale 12000 – 240 RPM Scale 3000 – 60 RPM Scale 12500 – 250 RPM Scale 3500 – 70 RPM Scale 13000 – 260 RPM Scale 4000 – 80 RPM Scale 13500 – 270 RPM Scale 4500 – 90 RPM Scale 14000 – 280 RPM Scale 5000 – 100 RPM Scale 14500 – 290 RPM Scale 5500 – 110 RPM Scale 15000 – 300 RPM Scale 6000 – 120 RPM Scale 15500 – 310 RPM Scale 6500 – 130 RPM Scale 16000 – 320 RPM Scale 7000 – 140 RPM Scale 16500 – 330 RPM Scale 7500 – 150 RPM Scale 17000 – 340 RPM Scale 8000 – 160 RPM Scale 17500 – 350 RPM Scale 8500 – 170 RPM Scale 18000 – 360 RPM Scale 9000 – 180 RPM Scale 18500 – 370 RPM Scale 9500 – 190 RPM Scale 19000 – 380 RPM

10,20,30,40,50,60,70,80,90,100 – The filter factor can be set to any of these values independent of your scale selection. Choose a filter setting that results in a smooth, high resolution RPM display. A filter setting too low for your setup will result in a “jumpy” display. RPM display will change at your base resolution and no smoothing will happen. Choose the lowest setting that results on a smooth display for greatest sensitivity of the reading.

OFF – the digital filter is switched off and the display will result in fastest update rates at the resolution dictated by your setup.

Technical specifications:

Display temperature range (operational): -20 to +80 degrees C Supply voltage: +8 to +18V. +24/28V with optional pre regulator. Supply current: 30mA/60mA (backlight off/on)

Rev counter input: Range: 0-20000 RPM. Minimum signal for stable display: 5Vpp. Fully A/C coupled, maximum voltage +/- 40V. RF noise filter plus Schmidt trigger based input.

Note: It is essential that a single wire be connected from the minus terminal of the instrument to the engine block. This wire must not be used to share currents with other electrical users as this can affect accuracy of readings.

Warranty: MGL avionics warrants their products for a period of one year from date of purchase against faulty workmanship. Warranty is limited to the replacement of faulty components and includes the cost of labor. Shipping costs are for the account of the purchaser.

Note for operation on supplies with inductive loads:

Any operation of electronic instrumentation on power supplies that are subject to high voltages caused by operation of inductive loads (starter motors, solenoids, relays) are required to be fitted with suitable protection. All Smart Singles are guaranteed to withstand temporary over voltage up to 40V without additional protection. We recommend that measures are taken to prevent voltage transients in excess of this limit. MGL Avionics recommends the fitment of a fuse in line with a 33V transorb (available from MGL Avionics at low cost) to protect electronic instruments, radios and intercom systems. Only one such arrangement is required for a cluster of instruments. Please note that product warranty excludes damages caused by unprotected, unsuitable or incorrectly wired electrical supplies.

Installing the RV-3

+5VDC output is not normally Ignition 2K2 resistor used. This is an unfused power coil supply output intended to supply pickup sensors or signal conditioners. In case it 20Volt Breaker is not used, please isolate zener diode the connection so it cannot short against anything. Ground

Cicuit shows Reference ground optional resistor Terminal strip (not supplied) to engine block and zener diode To other instruments as overvoltage protection. This Black may be required Blue if older contact breaker Power ignition systems switch are used. Red Fuse Positive supply (+12V from battery) Brown Suggested fuse rating: 1.0 A slow blow

Cannon D-9 connector

Cannon D-9 connector pin mapping and cable colors Pin 9 Pin 6 1 - ground - Black 2 - nor used 3 - not used Pin 1 Pin 5 4 - not used 5 - RPM pickup - Blue 6 - power (+12V) - Red 7 - +5VDC power out - Brown 8 - not used 9 - not used

Installation of the RV-3 is quite straight forward in most cases. The above drawing shows a typical connection for a standard “old fashioned” contact breaker system. Most electronic ignition systems are very similar, the only difference is that the breaker has been replaced with a semiconductor switching device. Most electronic ignition modules have an output terminal intended for connection to a rev counter. This sample circuit suggests a 2200 ohm resistor (2K2) and a 20V zener diode. Note that the zener diode is a polarized device, install with the band marker as shown. This small circuit should be installed if older contact breaker ignition systems are used as it is possible for these systems to generate very high voltages over the contact breaker. This could potentially damage the instrument if no protection is used. The components can be obtained from any electronics parts shop and are very inexpensive. Most other sources of RPM pickup do not require any further protection.

The RV-3 input is quite universally usable. For example, it is common to connect a hall-effect sensor using the +5V line to supply the sensor. A small magnet it then mounted on a shaft (for example rotor shaft of a helicopter) and the hall effect sensor switches every time the magnet passes the sensor.

The RV-3 needs a typical voltage swing of about 4 to 5.5V minimum to operate and the input is A/C coupled for easy installation. This means that the voltage signal may have a DC voltage superimposed without affecting the instrument. For example, if you have a signal that varies in voltage from 5V to 10V with every pulse, it can be used with the RV-3.

For installations such as with the Rotax DCDI two-stroke engines, the rev counter input is simply connected to the grey rev counter wire from the engine. These engines produce six pulses per rev (set this up in the relevant menu item).

Most engines produce 0.5, 1 or 2 pulses per revolution. This needs to be setup in the “Calib” menu item.

Please note: The 5V supply line is unprotected and intended only for the supply of hall- effect, optical or geartooth sensors. Connecting any voltages (such as the 12V supply) to this line will destroy the instrument. The 5V line may supply currents of up to 30mA. Should your sensor require greater currents you must supply it from another source.

Various pickup / sensor installation possibilities

Note: On Rotax DCDI ignition systems it Grey rev counter wire may be required to

+5VDC install a ballast RPM resistor as shown. A

GROUND typical value is 220 Ballast ohms. Many resistor installations can omit this.

Brown wire (engine block - ground)

Rotax DCDI setup (Ballast resistor optional)

2K2 resistor Typical hall effect sensor installation +5VDC detects the passing RPM of a magnet suitably GROUND fixed to prop flanges Magnet or shafts.

Hall effect sensor

Magnetic pickup with Hall effect sensor

White Red 1K resistor The gear tooth sensor is a popular +5VDC pickup used on the RPM pre-rotation gear of a GROUND gyro plane. (rotor speed No marking indication)

Honeywell gear tooth sensor

Magnetic pickup with active gear tooth sensor

220, 330 or 560 ohm resistor

+5VDC The optical reflective RPM pickup can provide a GROUND simple means of contactless RPM sensing in difficult installations.

2K2, 3K3 or 4K7 resistor

Optical, reflective sensor